The present invention relates to the improvement of a refrigerant cycling apparatus for use in an air-conditioner for obtaining a high or low temperature.
A conventional refrigerant cycling apparatus for obtaining a high or a low temperature has a plurality of refrigerant cycling devices are connected with each other in cascade type. In this refrigerant cycling apparatus, a high-boiling refrigerating component is enclosed in a cycle positioned in a higher stage and a low-boiling refrigerating component is enclosed in a cycle positioned in a lower stage. Further, a heat exchanger is provided to perform a heat exchange between the evaporated refrigerant in the higher stage and the condensed refrigerant in the lower stage.
In this apparatus, since the high-boiling point refrigerant is enclosed in the higher stage cycle, a high temperature is obtained with the vapor pressure lowered in the condenser in the higher stage. Since the low-boiling point refrigerant is enclosed in the lower stage cycle, a low temperature is obtained in the evaporator in the lower stage without generating a negative pressure.
The above-described conventional apparatus is suitable for obtaining a higher temperature or a lower temperature. But the heat exchange between the evaporated refrigerant in the higher stage and the condensed refrigerant in the lower stage is performed to reliably separate the high-boiling point refrigerant enclosed in the higher stage cycle and the low-boiling point refrigerant enclosed in the lower stage cycle from each other. Therefore, the evaporation temperature of the refrigerant in the higher stage is lower than the condensation temperature of the refrigerant in the lower stage. Therefore, compressors provided in the higher and the lower stage cycles are operated with a large compression ratio. Hence, the conventional apparatus is operated with a low efficiency.
In recent years, there is a growing demand for the development of a refrigerant cycling apparatus capable of supplying hot water and air-conditioning the temperature of a room rather than an apparatus just for supplying hot water or an extremely low temperature. However, in the conventional apparatus comprising a plurality of refrigerant cycling devices, the condenser in the higher stage is capable of serving as a means for supplying hot water as well as a heater, however, the apparatus is large-sized because a high-boiling point refrigerant has a low heating performance.